Sigma
by eleanoralovesananias
Summary: The DoctorDonna is a woman with two halves. One old, one young; one who remembers, one who does not. Together, they make up a being taken from between the Doctor's twelfth and final incarnations, united by one desire: revenge. Their quest will bring together the Doctor, old friends, older enemies, and one young man who is not quite either, and whom no one expected to see again.****
1. The Other Half

_"It's a brain. A hind brain. ...born with a secondary brain... you cut that off, you wouldn't be Donna anymore."_

 _"Like a lobotomy."_

 _"The circle must be broken... the circle must be broken..."_

 _"The subconscious reaching out."_

 _"Funny thing, the subconscious... takes all sorts of shapes... revenge... anger..."_

 _"Yeah, very you... always a death at the end."_

 _"One will still die..."_

 _"Binary, binary, binary, binary, binary, binary, binary, binary - I'm fine!"_

 _"I want to stay."_

 _"...I can't go back. Don't make me go back. Doctor, please, please don't make me go back!"_

 _He's inside her mind._

 _She doesn't want him there._

 _She is_ too _weak to fight._

 _As everything slides away into darkness, she can hear the Ood sing._

 _"Doctor, Donna, friends."_

 _But not anymore._

 _"The circle must be broken."_

 _"The subconscious reaching out..."_

 _"Revenge..."_

 _"Anger..."_

 _Revenge..._

 _Anger..._

 _Revenge..._

When she wakes up, she has a headache something awful. But what really disconcerts her is that her fists are clenched and trembling, her jaw constricted, and the strangest feeling of fury is sitting on her chest.

It's unlike her. In her daytime life, she really cares very little about much else than her friends, the newest celebrity gossip, and annoying Nerys. But sometimes when she wakes up in the morning, the remnants of another life, darkness and ash and fire, cling to her mind. She has this strange feeling of loss.

She shakes her head to clear it and pulls off her nightgown, throwing it in a heap on the floor. Who cares? She spends almost half an hour picking out an outfit; looks are important, and she has hardly any nice clothes. She walks down the stairs by rote, her eyes on her cell phone.

"Good morning," her mother says, trying to be nice but very out of practice. She glances at her for a second; lately her mother has been acting odd, like she's trying to establish a connection; well, too late. She doesn't reply.

"Good morning, love," her grandfather interrupts the awkwardness. She smiles gratefully and hugs him. Behind her, her mother tries not to cry. She doesn't notice.

She sweeps out the front door. A lone man walking by does a double take. She glares at him, and he blushes and walks quickly on. As she heads to work, people stop to stare. A woman says to her daughter, "See her? She's confident. Not so hard, is it?"

She doesn't realize how long her strides are, or how high she holds her head, or the queenly sternness with with she fixes people, the self-assuredness that makes people instinctively listen to her. She wonders why people are staring at her. Does she have something on her face? She knows she's ugly, but she's never gotten looks like these before, except from the creeps on the corner. She gives the fat woman on the bus her signature glare, and the woman turns beet red and buries her face in her newspaper.

When she gets home from work, she flops down on her bed and stares at the ceiling. Her head is pounding. It does that often, now. She knows she should probably go downstairs and grab a Tylenol, but she is tired, so tired. She doesn't know why she is alive, and she doesn't particularly want to be. There is something she is missing. She sighs, knowing that everyone feels like this sometimes, and pulls her pillow over her head.

She didn't mean to fall asleep, but the next thing she knows she wakes up screaming.

She's not screaming with fear, but rage, more rage than she knew she could hold, and her body feels weak and fragile before the fire of her mind. It takes her a few minutes to notice that she is pounding the walls with her fists, howling with fury at someone she can no longer remember. Someone has ripped her open, turned her inside out, and taken out all the best of her, and she wants it back. She wants it _back_. Her eyes and lungs feel hot and the roots of her teeth burn. She begins to sob, not knowing where all this despair and pain has come from.

Her grandfather's hands are on her back, frantically trying to calm her down. "Donna! Donna, what's wrong?" She turns and buries her face in his chest, unable to say anything.

It takes a few minutes before her parents are able to calm her down. She sits at the dining table, a mug between her hands, staring into space.

Sylvia Noble and her father Wilf watch nervously from their kitchen as their child and grandchild, respectively, stares off into what seems to be an unimaginable mental distance.

More than anything else, they want to help, to know what's wrong, but they are too petrified of what too many questions could do to her. They each stand all too still, somehow believing that any motion could set her mind aflame.

The words come out of Donna's mouth without her really thinking about them. Something seems to enthrall her in times like these, more and more often. The strangest part of it is that she doesn't mind, because the strong woman who takes hold of her inside and steers her quietly, with a sense of purpose she has somehow lost, feels to be more her than she is.

How this is possible, she doesn't know. She accepts it, does not question, and is unaware of how this detachment saves her life many minutes out of the day. So she speaks, or lets the woman within her speak; it's the same to her, really.

"Granddad, what does it feel like to kill?" she asks absentmindedly.

Her grandfather reacts, horrified, at the question. She fails to notice, too intent on the empty spaces within her.

 _Kill who?_ asks the Donna-half of Donna.

 _The man who took you away from me,_ the strong, confident, angry half - the Doctor-half, though she does not know it - replies.

 _But I'm right here,_ she points out, confused. She just barely registers that her mother is now crying, her grandfather holding her gently and trying to be reassuring while staring helplessly at his grandaughter, who stares ahead of her in a trance with eyes he does not know.

 _True enough,_ the Doctor-half answers happily, almost smugly, before her voice changes with bitterness and repressed rage. _Yet,_ _you don't know who I am._

 _Who are you?_ the Donna-half asks timidly, and she is surprised and afraid because she has never been timid, and now it seems that all the stubbornness and fight has gone out of her.

 _I am your strength, the power inside of you, the one he tried to take away,_ is the Doctor-half's response. It rings true instantly, and she accepts it. But she has the feeling there is more the woman is not telling her. She begins to question, tries to dig, to remember.

There is a short flash - a man in a blue suit, staring at her concernedly. "You really don't believe that, do you? All that attitude, all that lip - _all that anger,_ she adds silently - 'Cause all this time, you think you're not worth it. I can see, Donna, what you're thinking."

Her head begins to ache and burn, and she can feel a sudden burst of panic from the strong woman. _"Don't! Don't - don't do that."_

 _Why not?_ the Donna-half asks petulantly.

 _If you remember now, your mind will burn and you will die. He took that too, because I - because_ he is _a self-indulgent coward who never saves the people who matter._ The woman's bitterness is palpable. _But he will pay, dear Donna-half. He will pay._


	2. The Refugees

Rose Tyler lounges on the couch, poring over yet another theoretical physics book. Her dark brown hair hangs over her shoulder; she stopped bleaching it blonde a while ago. Her brown eyes are threaded with milky whitish-gold as an unfortunate side effect of so many physically straining dimension jumps, but she stubbornly focuses on keeping the words and diagrams in her fading vision.

She reaches over to the side table, eyes still straining over the book, and takes a sip of hot tea. She does it without looking. After so much time feeling the emptiness of the Void, the empty-cold which was so much colder than air-cold, she has adapted to feel the slightest bit of thermal energy, and the hot tea, wrapped in several thick rags so as to avoid burning her heat-sensitive skin, is easily found without the use of her eyes.

The formula she's trying to figure out swims and wriggles in her vision, and she gasps slightly and presses her hands over her eyes. They burn, badly. "John!" she shouts. "JOHN!"

John Smith-Noble (he's still deciding which last name to use) is already loitering, hesitating, outside of the the living room. At hearing her shout his name, panic audible in her voice, he rushes in to find her doubled over, the book forgotten on her floor, clutching her eyes.

He kneels in front of her and holds her by the shoulders, trying to see her eyes, but she has both hands across them and is crying out in pain. Hating to have to do this, he forces her hands away and uses his clean fingers to widen them, doing a quick examination. The milky gold bands have expanded and turned slightly pink; a sure sign that she's managed to inflame them. Again.

His fairly new human instincts are to stay and hold her until she stops screaming, but his much older Time Lord knowledge tells him otherwise. He pulls her into a quick, reassuring hug before jumping up and running to the kitchen, trying to not to shudder at the unfamiliar feeling of his human knees. He pulls open a drawer and searches in it for a few precious seconds before pulling out a small eyedropper and a bottle of bluish liquid.

It takes a few minutes, but soon enough Rose is taking deep breaths, the pain gone. John, meanwhile, sits down and puts his head between his knees, focusing on not vomiting.

He can physically feel the human adrenaline rushing in cycles from his human adrenal glands into his human bloodstream and all over his human body, making his human muscles contract, his breath come faster, and his single heart race. The feeling is nauseating, but he doesn't cry out. He hasn't cried out in a month now. The doctors tell him that's a sign that he's finally getting used to it, but they warn him that it will most likely be years before his body will fully adjust to being human. He hasn't told Rose that he doesn't believe them. This does not feel like he can or will 'adjust.'

Rose's thin, wiry arms wrap around him and gently squeeze, her head resting softly on his back and her dark hair spilling across his narrow shoulders, sending life-giving oxytocin through his human brain. He reaches up and pets her, running his long fingers through her hair. Rose always knows when he needs physical contact and when he needs space, what he wants and what he is thinking. She always has, since he was a Gallifreyan Time Lord, since he had an entirely different face and was fresh out of a long and bloody war.

Perceptive, that's how he would describe her. He knows that after her original father died, she took care of a family from the time she was a small child. He knows that her incredible emotional fortitude is the result of years of loneliness and responsibility. And he knows that she fell in love with a swashbuckling Time Lord who could take her on adventures across the galaxy, who could rescue her and let her be the princess in the tower when no one else had ever bothered. And he knows that he is not that man, and he can't give her that. All he can give is his pathetic human _forever_.

"You all right?" she asks, jolting him out of his thoughts.

He smiles at her. "I'm all right. I'm always all right," he adds before he can stop himself, even knowing that Rose has seen through that one since the day they met.

She frowns slightly, furrowing her brow, and silently, comfortingly pats him on the back. She doesn't know what's wrong, but he is her Doctor and she will always be by his side. Seeing that he is uncomfortable, she changes the subject. "So," she remarks, "you got here fast. What, were you just hanging about in the doorway?"

He shifts. "Actually, I was coming to talk to you."

She tilts her head, allowing her hair to fall across her face. "What about?" she asks brightly, expertly concealing her concern.

"Our... marriage." He is still not quite comfortable with the word, and less so with applying it to Rose.

She nods, chewing on her bottom lip as she often does when thinking. "Is September too soon? Don't worry, I completely understand. New body, new species, new universe... it makes perfect sense that getting married only a couple months later would be too much. I'm in no hurry. I'm happy to be your friend until you're ready to be anything more."

She gives that tongue-in-teeth smile, and his heart melts. That, at least, hasn't changed. He smiles back at her and gladly responds, "No. September is fine. Marrying you is going to be the best thing that's ever happened to me, and if an autumn wedding is what you want, I for one am not waiting another whole year." He clears his throat. "I actually wanted to talk about our last name."

Now her excitement is real. "Oh, have you finally decided? Took you long enough," she teases. "So which am I gonna be? Mrs. Smith or Mrs. Noble?"

He takes a deep breath. "Well, human ideas about names are so different from Gallifreyan ones, I've been doing some research. And what I've learned is that surnames are passed down through family. You would have the same surname as your parents, and it's a way of marking family allegiance." He looked at her out of the corner of his eye, gauging her reaction. She looked interested, but clearly was not following his point. He took a deep breath and continued. "The reason a married woman usually takes her husband's surname is because it's a way lf marking that she is now part of the husband's family."

He hesitated. "But, well... I don't actually have a family... at this point." It's hard to get that out. He feels as if he is choking on the words. He rushes on. "So, my last name, no matter what I decided, wouldn't carry the same weight. And really, it's you who's - who has welcomed me into your family, and your home, and your life." He looks shyly up at her. "So, with all that... I was thinking, that maybe... I could be John Tyler."

He watches as her rounded mouth falls open slightly. Slowly, her eyes sparkle and she smiles openly. "I can't believe how sweet you are sometimes, you know that?"

Her face becomes serious. "I would be honored to welcome you into the Tyler family."

It takes a second before he grins, the real, ear-splitting grin that he used to wear so often when he was a Time Lord. "Brilliant!"

Rose doesn't fail to note how long it's been since he's smiled like that. She grins back, tongue in teeth, and tackles him in a hug.

He laughs surprisedly and hugs her back. For a moment, things like blindness, species, mortality, marriage, and the ever-present worry that they have each changed too much to be right for each other anymore take the backseat to the momentary bliss of each other's company. They laugh, cuddle, talk about little things like the wedding cake and the honeymoon, and John reads to Rose out of the theoretical physics book in funny voices. They say goodnight and head to their separate bedrooms, a concession to John's discomfort with his human body.

Rose curls up under a thin sheet, warm enough without the heat of the blankets. She used to sleep stretched out, hands underneath the pillow, but now she prefers to sleep in the fetal position, chin tucked in and hands protectively on her head as if warding off blows. She has learned to will herself not to dream. She lets her eyes fall contentedly shut, allowing herself for the first time to imagine a happy life with her Doctor, a _forever_ just for them. In a few minutes, she is quietly asleep.

John climbs into bed, exhausted from the day's worries, and stares up at the ceiling. He tends to sleep on his back now, a habit he can only assume he picked up from Donna, since he always used to sleep stretched out on his stomach with his arms curled around the pillow. He's not so comfortable now; he likes to know for sure that no one is behind him in the night. A human house is not nearly as safe as the TARDIS, or as familiar. He never thought he needed familiarity, but he was obviously wrong.

He counts the places where the plaster makes pointed mounds on the ceiling as he restlessly puzzles over the Skasis paradigm that is his life: a never-ending maze that eternally seems almost completed, but never is. Perhaps he needs more human imagination. But that can't be true: he has more than enough imagination to have counted 43 different ways Rose could leave him, and he never dwelled on those things before. Maybe he just has too much _time._ Is this why humans work so much? He had always considered human imagination amazing, but in practice it seems just exhausting.

Still turning over his thoughts like an uneasy player at cards, his breath comes slower and he is asleep.

The darkness of sleep opens up to reveal a dream. Donna is standing at the sink washing the after-dinner dishes. Her parents watch her from the dining room, their eyes frightened. In the dream, he can hear her thoughts, like he used to be able to when they were in the same universe.

 _What do we do now?_ she asks - herself? It's odd, but there seems to be what is almost another presence here, hazy, not quite real. _Just wait?_ He can feel her scorn at the idea, and he half-smiles in his sleep. Her impatience reminds him of his own, back when the very idea of living in a house, much less with a woman, was death itself to him. How times have changed, for better or for worse.

 _We wait, and we plan. Better to arrive late with a plan than early without. Patience, dear Donna-half._ The voice is loving yet also mocking, with the tone of an overexcited child and a cynical veteran at once. Brand new, and yet paralyzingly familiar.

He's never felt a chill like this run down his spine. Watching Rassilon rave about the Final Solution, the moment when he realized the Master was still alive: these came close. But this...

This is different.

This is primal, coming from the depths of his memory, his unconscious, from the parts of himself even he is afraid of. He doesn't recognize the voice, but he _knows_ it. Not John. _The Doctor._

This is quickly turning into a nightmare. He turns, twists, tries to wake up, but he is trapped again by Donna's next thoughts.

 _But what am I supposed to do? You're such a genius, so you sit there and think of some brilliant revenge plot, but I just have to... what? Wash dishes? Act normal?_

 _You still don't understand how important you are. For one, you house me. But you're important even on your own. The threads are still pulling together. The prophecy will unfold, and a Hybrid is nothing, not even that, without both halves._

Absolute terror courses through the Metacrisis Doctor's human veins. He chokes on his own gasping breaths, tries to scream out for Rose, and manages a low groan.

Rose has been a light sleeper for some time now, the same amount of time since she began looking over her shoulder at every sound. She is up in an instant, before she even recognizes her fiancé's cries. Another quiet moan of fear is audible from the next room.

The fugitive's instinct takes over for thought, and she has a bedpost in her hands, the bed behind her splintered and leaning as she hears the bedsprings in the other room shift and every sense goes on alert.

Her knees bend for stability, toes apart for endurance, shoulders lowered for strength, chin up for focus, wiry muscles tight and breathing slow, deep, and quiet for maximum oxygen with minimum sound.

How many of them are there?

She can't hear the footsteps.

No human can suppress their footsteps, not really, without training. _Nonhuman, or professional._

Eyes focus on one spot, channeling all energy into hearing and touch.

There is no half-silent _whoosh_ of bodies through the air, or low breathing.

No heat, no warm flesh, no fluctuating point of temperature marking the heart. _Mental attack._

No emotion accompanies any of this. She is in survival mode, an empty space beyond emotion. She adapts fluidly to the new information. The bedpost goes in one hand. Mental armor goes up. Telepathic weapons are being prepared.

She enters John's room. He is writhing on the bed, fear on his face.

She crouches, drops the bedpost, leans over him and touches her fingers to his temples, fully prepared for an onslaught.

He's dreaming. It's a dream.

She exhales suddenly, and thought and feeling come racing back. She stands there, holding a thick wooden bedpost that she ripped off of her bed with her bare hands, feeling exhausted with adrenaline. She stares down at him, mouth slack and taking in air, while he stares, woken by her telepathic contact, confused, sleepy and frightened, up at her.

She drops the bedpost from her clammy hand and kicks it under the bed before he can see it. "So. You had a bad dream," she states, trying to cover for her flushed face, panting, and the unexpected mental probe she'd just sent into his mind while he was sleeping.

He blinks, not sure if she is real, afraid to touch her in case she disappears and he is back in that awful dream, the voice in Donna's head gleefuly tormenting him. "Yes," he whispers. "A terrible dream. Just a terrible dream."

At his tone, she melts and drops down on the bed, catching him up in a soul-warming hug. Rose rocks him and hums an old tune. His arms rest around her. Neither one of them has any idea what their presence means to the other.


	3. The Misanthrope

The young man walks across a sand-blasted plain. There is a backpack on his back, which contains all the clothes, valuables and possessions he had been able to stuff in it while the clock counted down the seconds before Torchwood arrived at his flat. His dark eyes stare ahead. He wears a dark green beanie pulled down hard over his forehead, and his clothes - a hoodie over a T-Shirt that says "Kiss the Chef and the God - I Just Made an Apple Pie From Scratch" and a pair of cargo pants - are filthy and tattered.

He stumbles, weak and tired from days of walking. Knowing by now not to push himself, he takes off his backpack and sits on it, resting his head on his knees and breathing deeply. When his head stops spinning, he pulls out his water bottle and allows himself a few precious drops.

He picks up a handful of sand and lets it run through his fingers, reflecting on how much his world has changed in a few weeks. Before, he would have been fascinated by the chemical composition of the sand, the geography of the place he's in, the countless stars above his head. Now he doesn't really care.

What he feels is not anger. It's too deep, too smoldering, dark and inward and hardened. Anger is what you feel when someone cheats on you, or when the jerk at the next desk gets the scholarship you worked hard for. This is hate.

This is what you feel towards the man who showed you the greed and the darkness and the ignorance inside the human heart, even in yourself and even in those you love, and then left you to the mercy of it. This is what you feel when someone takes your innocence forever, in a way you can never just "move on" from. This is the feeling of misanthropy and desolation with no forseeable end in sight.

The young man stares ahead and wills that feeling to coalesce inside of him, making it something he will never forget. If _The Doctor_ wants to tangle with human depravity, well, he'll get what he wants. He'll learn to fear humanity in all its hate- and avarice-filled glory. If the young man is after all a monster, at the very least he'll have the satisfaction of being The Doctor's monster.

He pulls himself up - slowly, slowly - dehydration, exhaustion, stress and hunger are not to be underestimated - shoulders his backpack again, and keeps walking. He's been walking for days now, or nights, really.

At first he tried walking during the day, assuming that the heat couldn't be that bad. His mother used to warn him that thinking he was invincible would be the death of him, and it almost was. Now when he sees the first hint of pink every morning, he slows, and when the sun peeks devilishly over the horizon, it's a sign that he isn't going to make it out today. Without a tent or any shelter, he tried at first to sleep stretched out on the sand, like the sheltered nerd he'd always been. He learned from _that_ one quickly.

He looks up at the night sky. The stars, scattered across the darkness like spilled salt - _unlucky_ , he thinks - are so bright and so countless that it's hard to remember they're separate from one another, much less their own suns with planets spinning around them, and living beings on some of them, and, somewhere out there, _The Doctor._ He could be looking at him right now, and he wouldn't even know it.

He gives a good hard glare towards the sky, just to be sure, and walks on.

* * *

 **Here I am! Third chapter's up, if you're reading this. I somehow managed to leave out the author's note on the first chapter, and it just didn't seem to fit with the mood of the second chapter, so here it is.**

 **This one's gonna be a doozy. Long, complicated, spanning all of New Who and maybe a bit of the classic, depending on how much time I have to catch up on the classic. All New Who companions, even the temporary ones and the one** **s who don't have the official title of companion, will be there, and again, the classic series is a 'hopefully.'**

 **I hope you enjoy it. Follows and favorites are nice, but above all, _review_** **. I want to hear your opinions, positive and negative, your (constructive) criticism possibly even more than your compliments, your favorites, your reflections, your thoughts about the show in general, your predictions, your suggestions, all of it. Hit me with it! I love you guys, I really do, and I want to hear your voices.**

 **If you think you know the focus of this chapter, please don't spoil it in the reviews. Leave a review telling me you think you know, and I'll message you so you can tell me who you think it is. Maybe I'll tell you in that message. Maybe I'll tell you if you're right or wrong. Maybe I'll just laugh maniacally. Who knows? ;)**

 **Anyway, have fun reading! The next chapter will most likely be up soon; I don't have a clear idea of what's going to happen, but I've been pretty inspired lately, so I'm hoping that won't be a problem. Stay with me, and enjoy!**


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